Geometry find length given altitude - Is my understanding correct?












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Question: For the the triangle $ABC$ , $BC=10$ and $AB=AC=13$. Given that $AD$ is a median and $BE$ is an altitude, find what $DE$ is equal to.



Well I construct the triable and I know that AD breaks BC into two equal parts of $5$. And that both $BE$ and $AD$ form right triangles.



If I look at triangle $BCE$, with angle $E$ being $90$ degrees, how can I say that $DE=DC=5=BD$



That's the answer, but I'm unsure as to why. I was leaning to thales theorem, where I can see $BDC$ as a diameter of a circle, that has angle $E$ being $90$ degrees. So they're all radius on the circle? Thus equal to 5?










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  • $begingroup$
    You are correct, any particular reason for you to question your solution?
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:49










  • $begingroup$
    I was wondering if my rationale behind using thales is correct? I'm not sure exactly why, as I drew the picture to scale and DE just looks equal to BD and DC. Does Thales here only hold if angle E is equal to 90?
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 3:53










  • $begingroup$
    If E was not 90 degrees, then the line BC would not be the diameter of $triangle{BCE}$'s circumcircle.
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:58








  • 1




    $begingroup$
    You can see proofs for what you used (the center of the circumcircle of a right triangle lies on its hypotenuse.) here
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 4:01












  • $begingroup$
    Ahh thank you so much! I understand now!
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 4:41
















0












$begingroup$


Question: For the the triangle $ABC$ , $BC=10$ and $AB=AC=13$. Given that $AD$ is a median and $BE$ is an altitude, find what $DE$ is equal to.



Well I construct the triable and I know that AD breaks BC into two equal parts of $5$. And that both $BE$ and $AD$ form right triangles.



If I look at triangle $BCE$, with angle $E$ being $90$ degrees, how can I say that $DE=DC=5=BD$



That's the answer, but I'm unsure as to why. I was leaning to thales theorem, where I can see $BDC$ as a diameter of a circle, that has angle $E$ being $90$ degrees. So they're all radius on the circle? Thus equal to 5?










share|cite|improve this question











$endgroup$












  • $begingroup$
    You are correct, any particular reason for you to question your solution?
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:49










  • $begingroup$
    I was wondering if my rationale behind using thales is correct? I'm not sure exactly why, as I drew the picture to scale and DE just looks equal to BD and DC. Does Thales here only hold if angle E is equal to 90?
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 3:53










  • $begingroup$
    If E was not 90 degrees, then the line BC would not be the diameter of $triangle{BCE}$'s circumcircle.
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:58








  • 1




    $begingroup$
    You can see proofs for what you used (the center of the circumcircle of a right triangle lies on its hypotenuse.) here
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 4:01












  • $begingroup$
    Ahh thank you so much! I understand now!
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 4:41














0












0








0





$begingroup$


Question: For the the triangle $ABC$ , $BC=10$ and $AB=AC=13$. Given that $AD$ is a median and $BE$ is an altitude, find what $DE$ is equal to.



Well I construct the triable and I know that AD breaks BC into two equal parts of $5$. And that both $BE$ and $AD$ form right triangles.



If I look at triangle $BCE$, with angle $E$ being $90$ degrees, how can I say that $DE=DC=5=BD$



That's the answer, but I'm unsure as to why. I was leaning to thales theorem, where I can see $BDC$ as a diameter of a circle, that has angle $E$ being $90$ degrees. So they're all radius on the circle? Thus equal to 5?










share|cite|improve this question











$endgroup$




Question: For the the triangle $ABC$ , $BC=10$ and $AB=AC=13$. Given that $AD$ is a median and $BE$ is an altitude, find what $DE$ is equal to.



Well I construct the triable and I know that AD breaks BC into two equal parts of $5$. And that both $BE$ and $AD$ form right triangles.



If I look at triangle $BCE$, with angle $E$ being $90$ degrees, how can I say that $DE=DC=5=BD$



That's the answer, but I'm unsure as to why. I was leaning to thales theorem, where I can see $BDC$ as a diameter of a circle, that has angle $E$ being $90$ degrees. So they're all radius on the circle? Thus equal to 5?







geometry euclidean-geometry






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edited Dec 5 '18 at 5:36









random123

1,2601720




1,2601720










asked Dec 5 '18 at 3:26









OnePieceFan123OnePieceFan123

62




62












  • $begingroup$
    You are correct, any particular reason for you to question your solution?
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:49










  • $begingroup$
    I was wondering if my rationale behind using thales is correct? I'm not sure exactly why, as I drew the picture to scale and DE just looks equal to BD and DC. Does Thales here only hold if angle E is equal to 90?
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 3:53










  • $begingroup$
    If E was not 90 degrees, then the line BC would not be the diameter of $triangle{BCE}$'s circumcircle.
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:58








  • 1




    $begingroup$
    You can see proofs for what you used (the center of the circumcircle of a right triangle lies on its hypotenuse.) here
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 4:01












  • $begingroup$
    Ahh thank you so much! I understand now!
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 4:41


















  • $begingroup$
    You are correct, any particular reason for you to question your solution?
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:49










  • $begingroup$
    I was wondering if my rationale behind using thales is correct? I'm not sure exactly why, as I drew the picture to scale and DE just looks equal to BD and DC. Does Thales here only hold if angle E is equal to 90?
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 3:53










  • $begingroup$
    If E was not 90 degrees, then the line BC would not be the diameter of $triangle{BCE}$'s circumcircle.
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 3:58








  • 1




    $begingroup$
    You can see proofs for what you used (the center of the circumcircle of a right triangle lies on its hypotenuse.) here
    $endgroup$
    – EvanHehehe
    Dec 5 '18 at 4:01












  • $begingroup$
    Ahh thank you so much! I understand now!
    $endgroup$
    – OnePieceFan123
    Dec 5 '18 at 4:41
















$begingroup$
You are correct, any particular reason for you to question your solution?
$endgroup$
– EvanHehehe
Dec 5 '18 at 3:49




$begingroup$
You are correct, any particular reason for you to question your solution?
$endgroup$
– EvanHehehe
Dec 5 '18 at 3:49












$begingroup$
I was wondering if my rationale behind using thales is correct? I'm not sure exactly why, as I drew the picture to scale and DE just looks equal to BD and DC. Does Thales here only hold if angle E is equal to 90?
$endgroup$
– OnePieceFan123
Dec 5 '18 at 3:53




$begingroup$
I was wondering if my rationale behind using thales is correct? I'm not sure exactly why, as I drew the picture to scale and DE just looks equal to BD and DC. Does Thales here only hold if angle E is equal to 90?
$endgroup$
– OnePieceFan123
Dec 5 '18 at 3:53












$begingroup$
If E was not 90 degrees, then the line BC would not be the diameter of $triangle{BCE}$'s circumcircle.
$endgroup$
– EvanHehehe
Dec 5 '18 at 3:58






$begingroup$
If E was not 90 degrees, then the line BC would not be the diameter of $triangle{BCE}$'s circumcircle.
$endgroup$
– EvanHehehe
Dec 5 '18 at 3:58






1




1




$begingroup$
You can see proofs for what you used (the center of the circumcircle of a right triangle lies on its hypotenuse.) here
$endgroup$
– EvanHehehe
Dec 5 '18 at 4:01






$begingroup$
You can see proofs for what you used (the center of the circumcircle of a right triangle lies on its hypotenuse.) here
$endgroup$
– EvanHehehe
Dec 5 '18 at 4:01














$begingroup$
Ahh thank you so much! I understand now!
$endgroup$
– OnePieceFan123
Dec 5 '18 at 4:41




$begingroup$
Ahh thank you so much! I understand now!
$endgroup$
– OnePieceFan123
Dec 5 '18 at 4:41










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